66 Treubia Vol. Ill, l 



in building materials or victuals for this temporary establishment. Mr. HanDL 

 himself told me that no rats were seen when he arrived on the island, but 

 they appeared later on. 



The finding of house rats at Zwarte Hoek (September 1920) proves 

 that the rats obviously spread over the island in less than three years. 

 A separate introduction at this point seems rather doubtful, Zwarte Hoek 

 being visited rarely, if ever, by anybody. Fishermen may touch here some- 

 times, but they never take so many things ashore during their short stay 

 that rats could be introduced. That, there are no rats on Verlaten Island N., 

 a much better landing place than Zwarte Hoek, seems also to justify the opinion 

 that the rats at Zwarte Hoek have come from the S. E. part of Krakatau. 



Mr. Groenewege, who visited Verlaten I. in December 1919, main- 

 tained that he has seen a small darkhaired carnivorous animal on this island 

 stealing through the glagah (Sacchariim spontane am). I was unable to 

 make out what this mammal could have been. 



The number of birds from Krakatau in 1920—1921 is two and a half 

 times that of 1908, but one must take into consideration that now two 

 ornithologists, Mr. BARTELS in April 1919 and Mr. SlEBERS in September 1920, 

 have paid special attention to the avifauna (see Appendix C). 



Besides, the species mentioned from Krakatau by JACOBSON in 1908 are all 

 resident forms except Tringoides hypoleucus. Of the 34 species of birds obser- 

 ved on Krakatau in 1920 — 1921 six are migrants, viz. /ls///r spec, ////7//z^6> 

 gnttnralis, Motacilla 'flava, Lantus super ciliosus, Tringoides hypoleucus ?ind 

 Nunienius phaeopus; two, Deniiegretta sacra and the Frigate bird, cannot 

 be ^aid to be true resident forms. Of the birds from Verlaten I , 38 species 

 altogether, we must deduct even a greater number to gt\ the true resident 

 forms. 



Migratory species noted on this island ^re Mirundo gutturalis,Motacilla 

 flava, Tringoides hypoleucus, Orthoraniphusniagnirostris{?)a.nd Ochthodronius 

 geoffroyi. As non-resident forms we have to consider those straying birds 

 such as Micropus pacificus. Butor ides javanica, the 5 -species of Terns and 

 the Petrel. After deducting all these species from the total number we 

 find 26 resident forms for Krakatau and 25 for Verlaten L, against 13 on 

 Krakatau in 1908. In this respect the number of birds on Krakatau has only 

 doubled. 



Two of the birds recorded by JACOBSON, viz. Alcedo beryllina and 

 Pycnonotus aurigaster, were not found again in 1920 — 1921. Some of 

 the birds mentioned as new to Krakatau are now so common that they 

 must have struck JACOBSON if they had been already present in 1908. 

 I suppose, therefore, that Eudynamis honorata, Calornis chalybea, Myris- 

 ticivora bicolor, Amaurornis phoenicura, and perhaps some others, are new 

 invaders which have reached the islands after 1908. The wood getting 

 thicker, the shrinking of the grassy plains and the maturing of fruit-bearing 

 trees, may have attracted the birds. 



